Biology subjects

Millan, A.

Publications and source records attributed to Millan, A..

4 recordsLinked to original sources

bioRxiv2024

Intraspecific variation of thermal tolerance in freshwater insects along elevational gradients: the case of a widespread diving beetle

Species distributed along wide elevational gradients are likely to experience local adaptation and exhibit high plasticity of thermal tolerance traits, as these gradients are characterised by steep environmental changes over short geographic distances (i.e., strong selection differentials). However, the prevalence of adaptive clinal intraspecific variation in thermal tolerance with elevation remains unclear, and this aspect has been poorly studied in freshwater insects. We explored variation in upper (heat coma temperature) and lower (supercooling point) thermal limits and acclimation capacity among Iberian populations of the widespread aquatic beetle Agabus bipustulatus (fam. Dytiscidae) across a 2,000-m elevational gradient, from lowland to alpine areas. As minimum, maximum and mean temperatures decline with elevation, we predicted that higher elevation populations will show lower heat tolerances and higher cold tolerances. We also explored whether acclimation capacity is positively related with climatic variability across different elevations. We found significant variation in upper and lower thermal limits among populations of A. bipustulatus, but no evidence of local adaptation to different thermal conditions along the altitudinal gradient, as relationships between thermal limits and elevation or climatic variables were in general not significant. Plasticity of upper and lower thermal limits was overall and consistently low in all populations. These results suggest conservatism of the thermal niche, which might be the result of gene flow counteracting the effects of divergent selection, or adaptations in other traits that buffer the exposure of populations to climate extremes. The limited adaptive potential and plasticity of thermal tolerance found here for A. bipustulatus imply that even generalist species, distributed along wide environmental gradients, may have little resilience to global warming.

ecology↗

bioRxiv2022

A chromosome-level genome assembly enables the identification of the follicle stimulating hormone receptor as the master sex determining gene in Solea senegalensis

Sex determination (SD) mechanisms are exceptionally diverse and show high evolutionary rates in fish. Pleuronectiformes is an emblematic fish group characterized by its adaptation to demersal life and its compact genomes. Here, we present a chromosome-level genome assembly of Senegalese sole, a promising European aquaculture species. We combined long- and short-read sequencing and a highly dense genetic map to obtain a contiguous assembly of 613 Mb (N50 = 29.0 Mb, 99% of the assembly in the n = 21 chromosomes of its karyotype). The correspondence between this new assembly and the Senegalese sole chromosomes was established by fluorescence in situ hybridization with BAC probes. Orthology within Pleuronectiformes was assessed by using the chromosome-level genomes of six important commercial flatfishes covering a broad phylogenetic spectrum of the order. A total of 7936 single-gene orthologues, shared by the six species, were used to identify syntenies in Pleuronectiformes and to explore chromosome evolutionary patterns in the order. Whole genome resequencing of six males and six females enabled the identification of 41 fixed allelic variants in the follicle stimulating hormone receptor (fshr) gene, homozygous in females and heterozygous in males, consistent with an XX / XY chromosome system. The observed association between fshr SNPs and sex was confirmed at the species level in a broad sample, which allowed tuning up a molecular sexing tool. Fshr demonstrated differential gene expression between male and female gonads since 86 days post-fertilization, when the gonad was still an undifferentiated primordium, concomitant with the activation of other testis and ovary marker genes, such as amh and cyp19a1a genes, respectively. Interestingly, the Y-linked fshr allele, which included 24 non-synonymous variants, expressed to a higher level than the X-linked allele at all stages. We hypothesize a molecular mechanism hampering the action of the follicle stimulating hormone that would drive the undifferentiated gonad toward testis.

genomics↗

bioRxiv2020

Sclerostin depletion induces inflammation in the bone marrow of mice

Romosozumab, a humanized monoclonal antibody specific for sclerostin, has been approved for treatment of post-menopausal women with osteoporosis at high risk for fracture. In several Phase III clinical trials, romosozumab decreased the risk of vertebral fractures up to 73% and increased total hip area bone mineral density by 3.2%. Previous work in 12 to 15-week-old sclerostin-knockout (Sost-/-) mice indicated that changes in immune cell development occur in the bone marrow (BM), which could be a possible side effect to follow in human patients. Our overall goal was to define the mechanisms that guide behavior of long-term hematopoietic stem cells (LT-HSCs) after exposure to an irregular BM microenvironment. SOST plays an important role in maintaining bone homeostasis, as demonstrated by the increased ratio of bone volume to total volume observed in Sost-/- mice. Here, we examined the effects of short-term sclerostin depletion in the BM on hematopoiesis in young (8 week-old) mice receiving sclerostin-antibody (Scl-Ab) treatment for 6 weeks, and the effects of long-term Sost-deficiency on wild-type (WT) LT-HSCs transplanted into older (16-22 week-old) cohorts of Sost-/- mice. Our analyses revealed an increased frequency of granulocytes and decreased frequency of lymphocytes in the BM of Scl-Ab treated mice and WT[->]Sost-/- hematopoietic chimeras, indicating myeloid-biased differentiation in Sost-deficient BM microenvironments. This myeloid bias extended to extramedullary hematopoiesis in the spleen and was correlated with an increase in inflammatory cytokines TNF, IL-1 and MCP-1 in the serum of the Sost-/- BM. Additionally, we observed alterations in erythrocyte differentiation in the BM and spleen of Sost-/- mice. Taken together, our current study indicates novel roles for Sost in the regulation of myelopoiesis and control of inflammation in the BM. Our animal studies strongly recommend tracking of hematopoietic function in patients treated with romosozumab.

immunology↗

bioRxiv2020

DISPERSE: A trait database to assess the dispersal potential of aquatic macroinvertebrates

Dispersal is an essential process in population and community dynamics, but is difficult to measure in the field. In freshwater ecosystems, information on biological traits related to organisms morphology, life history and behaviour provides useful dispersal proxies, but information remains scattered or unpublished for many taxa. We compiled information on multiple dispersal-related biological traits of European aquatic macroinvertebrates in a unique resource, the DISPERSE database. DISPERSE includes 39 trait categories grouped into nine dispersal-related traits for 480 taxa, including Annelida, Mollusca, Platyhelminthes, and Arthropoda such as Crustacea and Insecta, generally at the genus level. Information within DISPERSE can be used to address fundamental questions in metapopulation ecology, metacommunity ecology, macroecology and evolutionary ecology research. Information on dispersal proxies can be applied to improve predictions of ecological responses to global change, and to inform improvements to biomonitoring and conservation management strategies. The diverse sources used in DISPERSE complement existing trait databases by providing new information on dispersal traits, most of which would not otherwise be accessible to the scientific community.

ecology↗